1. Field of the Invention
The present invention relates to a control system of a synchronous motor.
2. Description of the Related Art
In a reluctance type synchronous motor, electric supply to a plurality of phase coils is sequentially controlled to induce magnetomotive force in a plurality of stator teeth to pull rotor teeth of a rotor, thereby rotating the rotor. Usually, an encoder is employed to control the rotation angle and the number of rotations of the motor. Such an encoder generates pulse signals that correspond to the rotation of the motor. The pulse signals are counted by a control unit to detect a rotation angle of the motor, so that electric current is sequentially supplied to the phase coils.
The encoder has a permanent magnet or other parts that are fixed to the rotor and Hall effect ICs or other parts that are fixed to the stator. Because the control unit has to count many pulse signals to calculate the rotation angle or position, it has to have a large computing capacity.